1. Field of the Invention
This invention relates to a novel monoatomic or monomolecular resist for use with a beam writer for the production of high resolution submicron circuit patterns on an insulating substrate.
2. Description of the Prior Art
The State of the Art of "Nanometer-Scale Fabrication" has been given with an excellent bibliography, as of 1982 [1]; wherein, it is stated on p. 3:
". . . electron, ion and X-ray exposure, . . . limitations of the resist . . . not those of the exposure system . . . set the ultimate limit on . . . resolution"; and:"The most commonly used resist for high resolution (&lt;100 nm or 1000A) is (PMMA) polymerthylmethacrylate. A resolution of &lt;50 nm or 500 A may be obtained with other resists . . . not well studied. "; and:"exposure of PMMA with a high intensity 50 kV field-emission electron beam source with a 20 nm. beam of 10.sup.-7 amps . . . takes 1 day (86, 400 sec. ) to expose a dense pattern on a 4" square (100 cm. .sup.2 or 10.sup.-2 m.sup.2), with additional time for stage motion and alignment. " PA0 Submicron lithography "using storage ring Xray sources may be closer . . . volume production . . . 1990's. A compact synchroton storage ring will be mated with a vertical stepper . . . will produce 12A wavelength at 630 MeV energy level. When MTED TO TILE COST storage ring, the XRS should have a resolution of 0.2.mu.m (2000A) . . . alignment accuracy to within 0.1 .mu.m (1000A). The stepper will expose wafers up to 8 in. (0.2 m) dia.
This is a speed of about 10.sup.-7 m.sup.2 sec; and a resolution of only 500 A.
The use of reactive ion etching to produce localized probes 1000A apart is reported [2] but this resolution is also small enough, and there is no increase in speed.
For the manufacture of Lepcon.TM., Elcon.TM. and such devices this speed is too small; and the resolution not small enough. A speed of about 0. 1 m.sup.2 sec and a resolution of 10A is required, not obtainable with these prior art devices.
A 10A resolution is reported [3]:
.multidot."Using a 1/2nm (5A) diam beam of 100 keV electron, we have etched lines, holes and patterns in NaCl crystals at the 2 nm. (20A) scale size. Troughs about 1. 5 nm. wide on 4. 5 nm centers and 2 nm dia holes have been etched completely through NaCl crystals more the 30 nm thick. " and "The scanning transmission electron microscope (VG Microscopes, Ltd. , Model HB5) in operation in the National Research and Resource Facility for Submicron Structures at Cornell University can produce up to 1 nA of 100 key electron in a beam dia as small as 1/2nm (5A). This beam current density of 1/2.times.10.sup.6 A/cm.sup.2 means that it takes only 10.mu.s to deposit a dose of 5 coulombs/cm.sup.2 in the sample." and "Two types of materials . . . alkali halides and aliphatic amino acids . . . can easily be vacuum sublimated or evaporated as uniform thin films . . . readily vaporized by electron beams. Using 100 key electrons a dose of about 10.sup.-3 C/cm.sup.2 is sufficient to etch through 30 nm of L-glycine, while a dose of 10.sup.2 C/cm.sup.2 is needed to etch through a similar thickness of NaCl." PA1 1. a high speed (about 0. 1 n.sup.2 /s) PA1 2. a large area (1 m.sup.2) PA1 3. a high resolution (less than about 5 A). PA1 4. a low cost (less than $250. 00/m.sup.2 -1986 prices. PA1 1. A small diameter image is formed from the electron emitter array by a demagnifying lens. PA1 2. One or two long focus electron lenses of the magnetic or electrostatic type are used resulting in negligible aberration. PA1 3. A large aperture lens may be used: to 30 mm. PA1 4. The focal length of the lens if 2. 5 m to 20 m, compared to about 2. 5 mm in a standard SEM. PA1 6. Writing speed is increased by the simultaneous scanning with a plurality of electron beams. For example: 2.times.10.sup.9 electron beams are scanned simultaneously to imprint the same number of identical patterns. PA1 7. The pattern is imprinted by an electron beam impinging on a surface coated with a monoatomic or monomolecular layer, which may comprise an electric double layer. The electron beam breaks the chemical bonds, changes the chemical or electrical characteristics, or ablates the layer. Prior art masking layers were usually about 300 A thick. The layer used herein is only 1/2% to 10% of the thickness of prior art coatings. Consequently the present method is more efficient than prior art methods, requiring considerably less electron beam energy per unit area.
In the latter reference the resolution is satisfactory but the speed is too slow.
Recently (1986) there has been a report on a new X-Ray lithography device [4]. This article stated:
A Field-Emission Scanning Transmission Microscope (STEM) has been described [5, 8]. A field emitter is employed to produce an emission area having a diameter of 30-300 A. One magnetic lens with a short focal length and low spherical aberration, is used to demagnify this source to a resolution of 2 to 5A on the specimen surface. The field emission gun and lens is mounted in an ultrahigh vacuum vessel that operates, at 10.sup.-8 to 10.sup.-7 Pa. When a short focal length lens is utilized to keep the system compact, aberration may be compensated by a "atigmator".
In these Prior Art Devices the speed is too slow for the rapid production of devices for the Lepcontm.TM.-Elcon.TM. Technology hereinabove specified.